Oval loudspeaker basket



Feb. 10, T970 A, L CQEN 3,494,444

` OVAL LOUDSPEAKER BASKET Filed June 5, 1967 5 Sheets-Sheet 2 4wd l. Caf/v L* By Wm...

Feb. 10, 1970 4.1.. com 3,494,444 l OVAL LOUDSPEAKER BASKET 5 Sheets-Sheet 3 Filed June s, 1967 M/ UM/H Feb. 10,1970 A. L. cor-:N 3,494,444

ovAL LOUDSPEAKER BASKET v Filed June 5, 1967 5 sheets-sheet i INVENTOR BY @du WML.

, Feb. 1o, 1910 M @EN 3,494,444l

' ovAL LOUDSPEAKER BASKET v Fiiea June s, 1967 5 Sheets-Sheet 5 Jla f i i .lwlrfffffff l 42M BY United States Patent O U.S. Cl. 181--31 5 Claims ABSTRACT F THE DISCLOSURE A loudspeaker basket and a method of manufacturing such a basket utilizing expanded metals techniques.

DESCRIPTION This invention relates to loudspeakers and, more particularly is concerned with a support structure or basket for supporting the diaphragm and magnet assembly of a loudspeaker and a method of manufacturing such a basket.

Generally, loudspeaker baskets are made by punching a blank from a sheet of metal (e.g. steel) and then forming the blank into a basket shape between a pair of dies. The blank is punched so as to provide, in the formed speaker basket, a central annular plateau region for mounting of a voice coil and magnet assembly and a peripheral liange for attaching the outer edge of thespeaker cone or diaphragm to the basket and for attaching the entire assembly to a speaker enclosure. Sufficient Inaterial is punched from the sheet of material so as to leave between the central annular region and the periphery of the blank generally radial ribs separated by substantial open spaces. The outside dimensions of the blank are substantially greater than the outside dimensions of the finished basket. During the forming process, the edge of the blank is restrained but not clamped tightly so that as the central annular region is displaced perpendicularly from the plane of the edge portion of the basket, metal from the edge portion is permitted to slip towards the center and, at the same time, the radial ribs are stretched slightly, the combined effect of edge slipping and rib stretching providing the total required displacement of the central annular region from the peripheral flange. In such a construction, the initial size of the lblank must be substantially greater than the outside dimension of the finished basket in order to accomplish the required displacement.

In accordance with the present invention, speaker baskets are manufactured utilizing expanded metal techniques which are substantially more economical of metal than the prior method. In the expanded metal method, the outside dimensions of the starting blank for a given size basket are only slightly larger than the outside dimensions of the finished basket and substantially smaller than the blank for the same size basket manufactured by the former method.

It is a particular object of the present invention to provide an oval loudspeaker basket (i.e. a basket for sup porting a diaphragm having an oval outer periphery) manufactured by expanded metal techniques.

It is a further object of the present invention to provide a method for producing an oval expanded metal loudspeaker basket.

In accordance with the present invention, a method of forming a support structure for a loudspeaker assembly comprises the steps of piercing a sheet of mechanically deformable material to provide, within an oval boundary, a central annular ring, a plurality of closely spaced concentric webs of substantial linear dimension disposed between the ring and the oval boundary and interconnecting radial web portions interconnecting each concentric web ICC alternately with adjacent inner and outer ones of the concentric webs, the radial and concentric webs defining concentric apertures having a linear dimension less than that of the concentric webs but substantially greater than that of the radial webs, rigidly clamping the edge portion of the pierced sheet outside the oval boundary, and displacing the annular ring along an axis substantially per pendicular to the plane of the edge portion while conforming the concentric and radial webs to a substantially smooth surface dened at one extreme by the oval boundary and dened at the opposite extreme by the annular ring for expanding the pierced sheet to form a loudspeaker basket.

In accordance with a further aspect of the present invention, a support structure for a loudspeaker assembly comprises an annular central portion, an oval peripheral flange, the oval flange having associated major and minor axes, and an apertured transition portion extending between the oval flange and the central portion, the transition portion comprising a network of relatively long, generally circumferential webs and relatively short interconnecting radial webs, a plurality of the long webs extending across the major axis and linking together segments of the oval flange disposed on each side of the major axis in adjacent quadrants of the oval.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation as well as addiional objects thereof will best be understood from the following description when read in connection with the accompanying drawing in which:

FIGURE l is a partial top view of an oval expanded metal loudspeaker support structure or basket constructed in accordance with the present invention.

FIGURE 2 is a front view, partially in section, of the support structure shown in FIGURE 1.

FIGURE 3 is a top View of a punched blank utilized for producing the structure shown in FIGURES l and 2.

FIGURE 4 is a diagrammatic sectional view taken through a punch press showing a step in the manufacture of the structure of FIGURES l and 2.

FIGURE 5 is a diagrammatic sectional view taken through a forming press showing a further step in the manufacture of the structure of FIGURES l and 2.

Referring now to FIGURES 1 and 2 of the drawing, the loudspeaker assembly comprises a magnet structure 10 mounted upon a central annular, plateau-like portion 12 of a speaker basket indicated generally by the reference numeral 14. A cylindrical voice coil assembly 16 is mounted by means of a exible suspension member 18 within a circular opening 20 in annular portion 12. Voice coil assembly 16 extends adjacent magnet structure 10 and is coupled by means of an electrical lead wire assembly 22 to a terminal board 24 mounted adjacent a barrel-shaped access opening 26a in basket 14. A similar opening 26h is provided diametrically opposite -opening 26a adjacent annular portion 12. A dust cap 28 is provided over the exposed` end of voice coil assembly 16. A speaker cone or diaphragm 30 having a central circular edge 30a and a peripheral oval edge 30h (i.e. an oval cone) is suspended between voice coil assembly 16 and a second suspension member 32. Suspension member 32 is retained within a peripheral fiange 34 by means of a gasket 36 and is fastened by means of a suitable adhesive against a lip 38. Mounting holes 40 `are provided in the lip between flange 34 and an oval boundary 42 of basket 14. Central annular portion 12, lip 38, flange 34, and the transition portion 14a of basket 14 all are formed from a unitary piece of metal such as steel or other suitable material.

The central annular portion 12 of basket 14 is displaced from the plane of lip 38 along an axis which is perpendicular to that plane (see FIGURE 2). Annular portion 12 and lip 38 are joined together by transition portion 14a which comprises a plurality of relatively long generally circumferential webs 44 joined together by relatively short interconnecting radial web portions 46. Webs 44 and interconnecting radial web portions 46 define a plurality of apertures 48 which are generally diamondshaped along the major and minor axes of `basket 14 but are irregularly shaped at points intermediate those axes. The outermost ends of the outermost ones of apertures 48 lie along the oval boundary 42. Stated differently, the webs 44 which extend across the major axis of basket 14 are joined together to form continuous links between the portion of oval boundary 42 on one side of the major axis and the portion of oval boundary 42 on the other side of the major axis.

Furthermore, it should be noted that While the radial webs 46 which lie along the major and minor axes of oval flange 34 are radially aligned, the radial webs 46 between such axes are not radially aligned. The positioning of the radial Webs is selected so as to provide a length for each segment of the long webs 44 sufficient to provide the necessary deformation thereof without fracturing. It has been found, for example, in the illustrated structure that a maximum permissible angle between two segments of webs 44 meeting at a common radial web 46 is approximately sixty degrees.

The manner in which the basket 14 is manufactured now will be described referring initially to FIGURE 4. In FIGURE 4, there is shown a sectional view through a portion of a punch press designated generally by the reference numeral 458. The principal parts of the press 458 for purposes of this description consist of a stationary apertured base plate 460 and a reciprocating head 462 having a plurality of curved punches 464, the punches 464 lying along concentric circles. Apertures 448 are provided in base plate 460 for receiving the punches 464 as head 462 is lowered and for permitting removal of material from a flat strip of sheet metal 450 which is placed upon base plate 460 for punching. In practice, sheet metal 450 may -be fed from a roll across base plate 460 from right to left in FIGURE 4 against an indexing stop (not shown) located at the left end of base plate 460. When the sheet metal 450 contacts the indexing stop, head 462 is brought rapidly downward such that punches 464 produce a predetermined plurality of apertures in sheet metal 450.

Where a large number of closely spaced apertures are required in the sheet 450, the punching operation preferably is carried out utilizing a multi-station punch press. For example, two separate heads, each containing onehalf the required punches (i.e. alternate rows of the required punches) and two separate base plates, each containing one-half the required apertures, may be provided in a single machine. In that case, as the sheet material 450 is fed into the press, the first punching operation will result in half the required apertures being punched in a first blank. The sheet 450 is then advanced and the second punching operation will result in a simultaneous punching of the second half (i.e. the alternate rows) of the required apertures in the rst blank and the first half of the apertures being punched in a second blank. In this manner, one blank will 4be completed for each punching operation after the first one. On the third punching sequence a cutoff device may be provided for cutting olf the irst blank which now passes out of the punch press. In such an arrangement, the tools (punches and base plate) more readily may be fabricated.

Referring to FIGURE 3, a at punched blank 50 is shown which is produced in the manner described in connection with FIGURE 4. The punched blank 50 is utilized, in accordance with the present invention, for forming the basket 14. ShQWn in FIGURES 1 and 2. In

4 FIGURE 3, elements of the blank Si) prior to forming which correspond to elements of the basket 14 (FIGURE 1) after forming are indicated by the same reference numerals as are used in FIGURES 1 and 2 with the addition of a prime notation following the numerals in FIGURE 3.

As shown in FIGURE 3, the blank 50` from which basket 14 is formed comprises a generally octagonal sheet of, for example, one thirty-second inch thick steel of aluminum killed grade. A plurality of discontinuous concentric apertures 48, a central circular pilot aperture 52 and a pair of modied rectangular apertures 26a and 26h having curved ends (preferably segments of concentric circles) and straight sides are punched in the sheet material. Continuous concentric webs 44 bounded at the inside by annular portion 12, at the outside by an oval boudary 42 (shown in dotted lines) and interrupted by apertures 26a and 26h are formed as a result of the punching. Webs 44 are joined together by interconnecting radial web portions 46 which extend between adjacent apertures 48. Central aperture 52 and two relatively small apertures 54 and 56 lying along the major axis of blank 50` serve as pilot holes for positioning blank 50 during the forming process as will be described below.

Referring to FIGURE 5, the manner in which punched blank 50 (FIGURE 3) is formed into basket 14 (FIG- URES 1 and 2) now will be described. In FIGURE 5, there is shown a sectional view through a portion of a forming press designated generally by the reference number 510. For purposes of this description, the principal parts of forming press 510 consist of a stationary base plate 512 including a male basket-forming die 514. A iloating ring 516 supported on an air cushion encircles the uppermost plateau region 518 of male die 514. Ring 516 is coupled by means of supporting pins 520 to a piston assembly 522 which extends within an air (or other hydraulic) cylinder 524. Pressure is maintained within cylinder 524 by means of a conventional pressurized air supply 526.

The forming press 510 further com-prises a movable female basket-forming die 530 and driving means (not shown) coupled to the female die 530 for reciprocating female die S30 along a vertical axis,

The punched blank 50 (shown in FIGURE 3) is located Vupon plateau regin 518 and floating ring 516 by indexing means (e.g. pin 528) for forming.

In the operation of forming press 510, base plate 512 and male die 514 remain stationary. Punched blank 50 is located on oating ring 516 and plateau region S18. Female die 530` is then moved vertically downward such that initial contact is made between female die 530 and blank 50 along the edge of blank 50 which rests on ring 516. The air pressure provided by supply 526 (eg. p.s.i.) is selected such that the edge of blank 50 is clamped between ring 516 and die 530 and thereby is substantially restrained from sideways movement. As female die 530 is advanced downwardly, the webs 44 and 46 of punched blank 50 (see FIGURE 3) are displaced and the apertures 48 between webs 44' are enlarged, thereby expanding blank 50 into `the desired basket shape (see FIGURE 1). Female die 530- is then lifted permitting removal of the formed basket. The dimensions of ring 516, rods 520 and dies 5114 and 530 are arranged such that the interconnecting webs 44 and 46 of the finished basket all lie along the smooth surfaces of the dies 514 and 53-0.

After removal from the forming press 510, the formed basket is trimmed along its outer edge and mounting holes 40 (FIGURE 1) and the larger central voice coil hole 20 are punched by means of a conventional vertical punch press.

In the final trimming operation, only a very narrow strip of material is discarded since, as was mentioned above, the outside dimensions of blank 50 are only slightly greater than the outside dimensions of finished basket. 1.4.. The increase in the dimensions along the surface of transition portion 14a required to permit vertical displacement of annular portion l2 from lip 33 is provided substantially solely by the rearrangement of the webs 44 and 46 during the forming or expansion operation. In a typical 8" x 12@ oval basket, the savings. in material realized by virtue of the present invention is of the order of twenty percent.

It should also be noted that, while the transition portion 14a, of basket 14 extends between a circular inner portion 12 and an oval outer boundary 42, the apertures 48 and the webs 44 (FIGURE 3) in the blank 50` all lie on concentric circles. Such an arrangement permits relatively simple and therefore not excessively costly manufacturing of the tooling (i.e. punches 464 and apertured base plate 460 of punch press 458) required for producing the punched blank 50.

What is claimed is:

1. A support structure for a loudspeaker assembly comprising an annular central portion,

an oval peripheral flange, said oval ange having associated major and minor axes, and

an apertured transition portion extending between said oval flange and said central portion, said transition portion comprising a network of relatively long, generally circumferential webs and relatively short interconnecting radial webs,

a plurality of said long webs extending across said major axis and linking together segments of said oval flange disposed on each side of said major axis in adjacent quadrants of said oval.

2. A support structure for a loudspeaker assembly according to claim 1 wherein 6 said interconnecting radial webs are radially aligned along said major and minor axes and are radially misaligned intermediate said axes so as to provide, for a desired spacing between said annular central portion and said oval ange, a substantially smooth, unbroken transition therebetween. 3. A support structure for a loudspeaker assembly according to claim 2 and further comprising first and second side ribs and an end rib defining at least one substantially barrel-shaped opening adjacent said central annular portion and extending radially along said major axis. 4. A support structure for a loudspeaker assembly according to claim 3 wherein each segment of said long Webs is of sufficient length to restrict the angle between segments joined at a given radial web to a value less than a fracturing value. 5. A support structure for a loudspeaker assembly according to claim 4 wherein said angle is less than sixty degrees.

References Cited UNITED STATES PATENTS STEPHEN J. TOMSKY, Primary Examiner U.S. Cl. X.R. 181-32 

